The growing popularity and proliferation of light bulbs formed with LED devices has directed attention to powering concepts. Incandescent light bulbs are primarily driven by voltage, whereas LED devices are primarily driven by current. This means that circuitry more complex than wires connecting a filament to a source of power is required, and if light dimming is required the circuitry becomes even more complex. Also this circuitry complexity needs to be packaged in a small space to allow an LED bulb to replace an incandescent bulb in a fashion similar to which has been used by the incandescent bulb, for instance screwing an LED bulb into an incandescent “light” socket.
The technologies used to create an LED power dimming capability appear to be wide ranging from power factor control to a switch mode control using a tapped buck configuration. The objective is not only to be able to reduce the illumination from an LED bulb, but to reduce the illumination smoothly and flicker free. In some cases an audible noise, for instance a buzz or whistling, occurs caused by physical components or PCB stress at high current flow, and an increase in dimming resolution is needed. These problems detract from the utility of a LED light bulb and the ability to dim the illumination resulting from the light bulb.
In U.S. 2013/0175929 A1 (Hoogzaad) a method is directed to regulating an LED current flowing through a circuit containing an LED device. U.S. 2013/0113386 A1 (Hariharan) is directed to an LED illumination system comprising devices and methods of driving an LED. U.S. 2013/0099684 A1 (Cheng et al.) is directed to parallel channels of LED devices using a pulse control signal. U.S. 2012/0062138 A1 (Wilson et al.) is directed to an illumination apparatus comprising a plurality of LED devices and a control system connected to receive dimmer-modulated AC line voltage. U.S. 2002/0167471 (Everitt) is directed to a pulse width modulation driver for an organic LED display. U.S. Pat. No. 8,441,202 B2 (Wilson et al.) is directed to a plurality of LED devices and a control system connect to receive dimmer-modulated AC line voltage to control the LED devices. In U.S. Pat. No. 8,362,706 B1 (Godbole) an apparatus and method is directed to control current through one or more LED circuits, wherein a compensation unit functions to offset errors. U.S. Pat. No. 8,358,084 B2 (Shin et al.) is directed to an LED current control circuit comprising a current detecting unit, a current adjusting unit and a current control unit. U.S. Pat. No. 7,999,491 B2 (Peng et al.) is directed at providing a high precision lighting control means to drive an LED lighting module.